[fpc-devel] FPC-JVM: Breaking up a cycle

[Jonas Maebe]

On 27 Aug 2011, at 00:16, Sven Barth wrote:

> There is a class AVView, a class AVViewGroup and an interface AVViewManager. AVViewGroup extends AVView and implements AVViewGroup. Also it defines a nested class InnerLayoutParam.
> 
> So far all is ok, but now the problematic part:
> AVView and AViewManager both contain a parameter and/or result value of type AVViewGroup.InnerLayoutParam.
> 
> Is there a way to solve this quite nasty circle?

Not in a clean way. The only way you can do it is by removing AVViewGroup.InnerLayoutParam from the AVViewGroup class and declare it as an empty class up front (empty because I don't think it will be handled correctly if you add methods etc to it and try to call those later):

  AVViewGroup_InnerLayoutParam = class external 'Android.V_add_rest_of_package_name' name 'ViewGroup$Layoutparam' (parentclass,parentintf1,parentintf2, ...)
  end;

And then replace all references to AVViewGroup.InnerLayoutParam with references to AVViewGroup_InnerLayoutParam.

It's a limitation of the Pascal language compared to Java (no way to refer to inner classes before the parent class has been defined), and even if we would choose to lift it somehow (e.g. by allowing something like "AVViewGroup.InnerLayoutParam = class;" as a top level declaration) I'm not immediately sure how we to implement that efficiently in the compiler.


Jonas